Fix atmosphere lighting issue for below ground geo

[mate-h]

Objective

• Fix atmosphere lighting issue for below ground geo

Issue reported in discord channel for rendering-dev by Jondolf@

Repro on f8a9f29

use bevy::{pbr::EarthlikeAtmosphere, prelude::*};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
    earthlike_atmosphere: Res<EarthlikeAtmosphere>,
) {
    commands.spawn((
        Mesh3d(meshes.add(Capsule3d::new(0.5, 1.0))),
        MeshMaterial3d(materials.add(Color::WHITE)),
    ));

    // Directional light
    commands.spawn((
        DirectionalLight {
            illuminance: 5000.0,
            shadows_enabled: true,
            ..default()
        },
        Transform::from_xyz(1.0, 2.0, 2.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));

    // Camera and atmosphere
    commands.spawn((
        Camera3d::default(),
        earthlike_atmosphere.get(),
        Transform::from_xyz(10.0, 2.0, 15.0).looking_at(Vec3::new(0.0, 0.0, 0.0), Vec3::Y),
    ));
}

Solution

• Clamp the position to the ground surface with a small epsilon before calculating occlusion from the planet

Testing

• Ran the atmosphere example with local changes to put geo below-ground

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Showcase

Before

After

[Jondolf]

Thank you!